1. Field of the Invention
The present invention relates to a quick-acting closure with sliding retaining-ring. Clamp-type, clutch-type, and also screw-type, or press-frame type closures are used as quick-acting closures for pressure vessels which have been utilized widely in the chemical industry, food industry and various other industries.
Furthermore, as a simple closure which does not quickly act, a retaining-ring type closure has also been used.
Recently, the use of pressure vessels whose covers are frequently opened and closed has been increasing in high pressure experiments, or high-pressure or super-high pressure commercial applications.
2. Description of the Related Art
FIGS. 4A and 4B show a conventionally used closure with a retaining-ring which is sealed by sealing means around the radially facing peripheral surface thereof (ASME SEC.VIII Div. 1, FIG. UG-34,(m), Some Acceptable Types of Unstayed Flat Heads and Covers). After a cover 1 is fitted into a shell 2, the cover is fixed by moving a segmental retaining-ring 3 (the ring is divided into eight segments 3a in the example of this drawing) to a position shown in FIGS. 4A and 4B and by positioning it in place. The horizontal movement a of the retaining-ring 3 is performed manually and the vertical movement b by a crane.
An explanation of the actuation of a vessel cover with the following specifications (as an example) will be given.
Vessel Dimension: Inside Diameter 500 mm.times.Inside Height 1000 mm PA0 Vessel Fabrication: Forging, Solid-Ring Type PA0 Vessel Material: ASME SA-723 Gr. 3 Cl. 3 PA0 Design Pressure: 1500 kgf/cm.sup.2 PA0 Test Pressure: 1800 kgf/cm.sup.2 PA0 Cover Type: Retaining-Ring PA0 Operating: Opened by hand PA0 Seal Material: Rubber-Ring PA0 Shell Thickness: 200 mm PA0 Shell Weight: Approx. 8 Ton PA0 Cover Thickness: 200 mm PA0 Cover Weight: Approx. 1 Ton PA0 Retaining-Ring Weight: Approx. 20 kg per segment
After the cover 1 is brought by a crane to the shell 2 to be fitted therein with a sealing projection 1a extending into the mouth of the vessel, the upper surface 1b is slightly below the level of the lower surface 2b of a retaining-ring receiving recess 2a opening out of the inner surface of the wall of the vessel 2. The retaining-ring segments 3a are then placed on the cover. When there is no pressure in the vessel, the bottom surface 3b of the segments 3a of the ring which are resting on the cover surface 1b will be slightly below the lower surface 2b of the recess 2a, as shown in FIG. 4C. Then they are moved manually slightly upwardly and in the radial direction to be positioned in place as shown in FIGS. 4A and 4B. Thus the cover of the vessel is retained in the closed position. High pressure (1500 kgf/cm.sup.2 in the example) is introduced and maintained for a certain time by a high-pressure pump through a liquid inlet nozzle 5, and then the vessel is depressurized. The internal pressure is retained by a radially facing seal 4 between the sealing projection 1a and the mouth of the vessel, which permits the cover 1 to be raised against the retaining-ring 3, which in turn abuts the upper surface 2c of the recess 2a, due to the internal pressure without raising the cover sufficiently far to break the seal at seal 4. Thereafter, when atmospheric pressure is once again reached in the interior of the vessel, the cover is opened by the segments of the retaining-ring 3, which are now only loosely engaged with the cover 1, being manually slid toward the center in the radial direction and the segments are lifted upward one by one to remove the retaining-ring. Then the cover is removed. The series of operations described above is repeated as a batch-process.
The most important point from the point of view of the operation efficiency is the time required for opening and closing the cover. In this example, approximately two hours are required. It is very important that the time for opening and closing the cover should be shortened to improve the operation efficiency.
Part of this time is consumed by the necessity for and difficulty in slightly lifting the segments to get them from the level of the upper surface 1b of the cover 1 to the level of the lower surface 2b of the recess 2a. Moreover, when internal pressure builds up in the vessel 2 and the cover 1 rises slightly, the segments 3a tend to be tilted and held between the peripheral edge 1c and peripheral edge 2d of the upper part of recess 2a in edge-to-surface contact, as shown in FIG. 4D, which is undesirable from the standpoints of strength requirements for the vessel and the ring segments and the lifetime of these parts. The increased stress on the parts due to the edge-to-surface contact shortens the life of these parts. Modifying the arrangement to raise the level of the upper surface 1b of the cover 1 either to the same level as the surface 2b or above the surface 2b, as shown in FIGS. 4E and 4G, to make it easier to slide the segments 3a into the recess 2a does not alleviate the problem because the clearance 5 between the level of the upper surface of the segments 3a and the upper surface of the recess 2a must be increased to make it possible to move the segments 3a into the recess 2a, as shown in FIGS. 4F and 4H.
As has been described, in the conventional arrangement, it is required that the segments of the retaining-ring be manually moved in the radial direction after the ring has been lowered on the cover by a crane. Therefore, the method has the following disadvantages.
1. It is necessary to manually attach or detach the heavy retaining-ring every time the cover is opened or closed. This is not desirable from the point of view of safety.
2. At the same time, it takes a lot of time for the cover closing the opening operation, resulting in considerable idle time in the overall operation, thus lowering operation efficiency.
3. Because of the edge-to-surface contact of the segments and the edge of the retaining-ring receiving recess, the stress on the various parts shortens the life of the apparatus.
4. Accordingly, the conventional arrangement has proved to be unsatisfactory for a quick-acting closure.